Liquid crystal display devices are widely used as display devices for displaying color images. Many conventional liquid crystal display devices display color images using color filters. Further, field sequential type liquid crystal display devices are known as a liquid crystal display device for displaying color images without using color filters.
Typically, a field sequential type liquid crystal display device is provided with a backlight including light sources of red, green, and blue, and displays three fields of red, green, and blue in one frame period. When the red field is to be displayed, a liquid crystal panel is driven based on red image data, and the red light source emits light. Then, the green field and the blue field are displayed in a similar manner. The three fields displayed by time division are combined based on an afterimage effect on an observer's retina, and thus would be recognized as a single color image by the observer.
In the field sequential type liquid crystal display device, the observer often sees colors of these three fields separated when a line of sight of the observer moves within a display screen (this phenomenon is called as a color breakup). Further, when an image moves quickly, an afterimage may be generated to cause blurring of the image or an unnatural motion of the image (this phenomenon is called as a judder). For suppressing the color breakup and judder, there have been conventionally known a method of performing frame rate conversion on image data, and a method of displaying a white field in addition to the red, green and blue fields. Apart from these methods, there is known a method of controlling the brightness of the backlight for each area in accordance with image data, as a method of reducing power consumption of the liquid crystal display device and increasing display contrast. The method of controlling the brightness of the backlight for each area may be used to suppress the color breakup.
As the field sequential type display device, the following techniques have been conventionally known. Patent Document 1 describes an image processing device for a time division color display device that performs frame interpolation processing (see FIG. 10). In FIG. 10, a motion detection circuit detects a motion direction and a motion amount of an image between frames of image data. A display position correction circuit corrects a display position of the image per field of each frame based on output of the motion detection circuit.
Patent Document 2 describes an image display device that controls brightness of a backlight for each area, and displays white, red, green, and blue fields (see FIG. 11). The image display device shown in FIG. 11 performs resolution reduction processing to input video signals Rorg, Gorg, Borg to obtain light emission patterns BLr, BLg, BLb of the backlight for each partial light emitting area. Then, the image display device generates partial driving video signals R, G, B by dividing the input video signals Rorg, Gorg, Borg by results obtained when diffusion processing is applied to the light emission patterns BLr, BLg, BLb, and extracts a common white component Wcom from the partial driving video signals R, G, B.